Ultradisintegration and agglomeration of minerals such as mica, products therefrom and apparatus therefor

ABSTRACT

Frangible or cleavable solids, such as mica, are disintegrated in oriented, high-velocity streams of a fluid medium so as to produce thin smooth-surfaced particles or flakes having a high specific surface area and a high ratio of length to thickness. The resulting particles or flakes are useful as agglomerants, fillers or pigments or can be agglomerated to form paperlike webs or solid discs or articles of other predetermined configurations, with or without added binder, either in self-supporting form or adhered to a substrate. Various methods and apparatus for such disintegration and agglomeration are also disclosed.

tts [l Unit Josef Ruziclm 55-25 98th Pince, Rego [Pan-lt, NSY. 1111368650,543

,lume 30, 1967 Sept. 28, 119711 [72] Inventor [21 Appl. No. [22] Filed[45] Patented [54] ULTRAUISUWTIEGTHUN ANU AGGLOWRATMUN @lll MINELS SUCHAS MECA, PRODUCTS THEMIFMUM AND APPARATUS 'llllillERlElfOh Il ll Claims,19 Drawing [52] 111.8. Cl. 2411/4, 241/5, 241/24, 241/39, 241146.06 [51]lint. Cl 002e 119/06 [50] hield ai Search 241/4, 46, 46.02, 46.04,46.06, 46.13, 79.1, 97, 266, 38, 20, 27, 5, 39, 24

[56] References Cited UNITED STATES PATENTS 3,087,482 4/1963 Haller241/4 X 3,l62,579 12/1964 3 ,240,203 3/1966 2,345,474 3/1944 Haverland..241/46.l3 X 3,206,127 9/1965 Morris 241/4 3,223,333 12/1965 Stephanoff241/5 Primary Examiner-Donald G. Kelly Attorney-Bums, Doane, Sweclter 8LMathis A'll'llMCT: Frangible or cleavable solids, such as mica, aredisintegrated in oriented, high-velocity streams of a fluid medium so asto produce thin smooth-surfaced particles or flakes having a highspecific surface area and a high ratio of length to thickness. Theresulting particles or flakes are useful as agglomerants, llers orpigments or can be agglomerated to form paperlilte webs or solid discsor articles of other predetermined congurations, with or without addedbinder, either in self-supporting form or adhered to a substrate.Various methods and apparatus for such disintegration and agglomerationare also disclosed.

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PATENIED seras m11 315083535 FWN@ VERY THIN (INVENTION) HQI@ T00 THICK N(PRIOR ART) I NTION I ULTRADISINTEGRATION ANlD AGGLOWRATION OIF MINESSUCl-I AS MICA, PRODUCTS TMEREOM ANI) APPARATUS TllillElRlElFOIt SUMMARYOF INVENTION This invention relates to the disintegration of frangiblesolids into ultrafine particles and the reagglomeration of suchparticles into desired products, to apparatus for carrying out suchoperations, and to various products obtained thereby. More particularlythe invention relates to the oriented disintegration of a mineral suchas mica into a multiplicity of fluidly suspended ultrathin particles orflakes and the production of new or improved products such as mica papertherefrom.

This invention generally is concerned with the splitting of easilysplittable or cleavable materials to form fine particles, and especiallythe cleavage of minerals such as mica into small, thin flakes or scaleswhich have active surfaces and which fall predominantly within arelatively narrow size range. The resulting products include micaparticles characterized by an unusually high ratio of surface tothickness.

The disintegrating or splitting equipment is intended primarily for thesplitting of mica but is also highly effective in splitting othermaterials, especially minerals, which liberate molecularly bound wateror water of crystallization upon heatmg.

The aforementioned materials can be used in many different ways. Forinstance, the free particles or unoriented, easily redispersibleagglomerates of such particles are useful as pigments and fillers forpaints or other coating compositions, for resinous plastics, forelastomeric compositions; or as adsorbents or carriers for othermaterials, etc. In the form of oriented agglomerates they are useful asinsulators or coatings in electrical equipment, as constructionmaterials, etc.

BACKGROUND OF INVENTION Mica forms a group of silicates, which areminerals characterized by their highly pronounced ability of beingcleaved along their basic crystalline plane while being substantiallyless susceptible to cleavage along the crystalline plane which issubstantially perpendicular to the first plane, and being still lesssusceptible to cleavage along any other plane. Consequently, this typeof mineral has crystalographically a platelike structure which is highlyflexible, resilient and strong and can be divided and subdivided intovery thin flakes or scales.

Mica as a mineral is found in nature in various crystalline sizes, largesizes being quite rare, and in various chemical compositions such asmuscovite, phlogopite, biotite, etc. Because of its excellent dielectricand mechanical properties, chemical stability and resistance to hightemperature, mica is used for various industrial purposes, the highestgrades of mica being used principally in the electrical industry as aninsulating material. Its properties and usefulness, however, differsubstantially not only depending on its basic type but even in a giventype the properties depend on the exact chemical composition. Thechemical composition of natural mica differs substantially, sometimeseven within a single crystal. Yet the exact chemical compositiondetermines the thermal resistance of individual mica crystals and whenthe critical dehydration temperature of a given piece of mica isexceeded, usually above 500 C., the mica becomes dehydrated and swellsup and disintegrates depending on temperature and duration of heating.Synthetic mica has similar characteristics and properties.

PRIOR ART Natural and synthetic mica crystals are relatively small whilemodern industrial requirements point increasingly toward large surfaces.For this reason the efforts in the art have increasingly been towardsplitting mica into flakes of ever smaller thickness and reintegratingthese thin flakes with or without the aid of binders into coherentsheets or leaves of large surface area. However, prior methods formaking products of large surface area from mica particles having athickness on the order of a few hundredths of a millimeter, c g., 0.010to 0.030 mm., have proved to be very laborious, the utilization of themica is relatively low and the resulting products are quite nonuniformas well as expensive. Moreover, they lack adhesive surface forces.

Methods of making sheets of large surface area from mica particleshaving a thickness on the order of less than 0.01 mm.

eg., about 0.002 to 0.008 mm. have been known for more than 50 years.However, poor physical and especially mechanical properties of theresulting products have prevented them from becoming commerciallyimportant. More recent methods such as those described by Heyman in U.S.Pat. No. 2,405,576 or by Bardet in U.S. Pat. No. 2,549,880 have achieveda certain degee of commercial signicance particularly because themechanical properties of the resulting products are better than those ofearlier products. However, though these processes are now more than 20years old they have never achieved wide use. They have only partiallysucceeded in replacing the older methods which resulted in particleshaving a thickness greater than 0.01 mm., because their physical andespecially their mechanical and dielectric properties still leave muchto be desired, their processing is difficult, 'the utilization of themica raw material is incomplete, and the operating costs are high.

Even when mica particles are to be used as pigments or fil- 1ers thetrend in the art is to require particles of ever smaller thickness, thatis, particles having the greatest possible surface area per unit weight.However, in requiring this there is also often the further requirementthat the particles should not exceed a specified maximum dimension andshould fall within a rather narrow particle size range. On the otherhand, especially in the case of particles having a small diameter, suchas l micron or less, the art has heretofore been unable to obtain highyields of particles falling within a predetermined narrow size range.The previously known mica particles at best had only very weak adhesivesurface forces.

OBJECTS lt is accordingly an object of this invention to prepare finesolid particles such as mica flakes having a high specific surface areaand other new or improved properties which make such particlesparticularly valuable as agglomerants or pigments and also in theproduction of aggregated products. Another object is to prepare improvedproducts by agglomeration of fine particles.

A still further object is to provide new or improved methods andapparatus for oriented cleavage of mica principally along its main planeof crystallization and secondly along one further plane ofcrystallization while limiting the cleavage or splitting along any otherplanes, so as to facilitate the production of particles or flakes havinga large specific surface area and a geometrically elongatedconfiguration with predominantly submicron thickness, on the order of afew tenths or even thousandths of one micron or less, permitting thesegregation of flakes having specified geometric dimensions, wherein theinvention permits recycling of insufficiently disintegrated mica piecesto be split further until particles or flakes having the specifieddimensions are produced.

A further object is to provide methods and apparatus for preparing andmaintaining a fluid suspension of the fine mica flakes, to besubsequently converted either into an agglomerate or into free flowingparticles to be used as a pigment or the like.

A still further and particular object is to provide apparatus andmethods for producing improved mica paper or other structures eithersolely from the fine mica flakes or from a mixture of such flakes withother conventionally used auxiliary materials such as binders, fillersand so forth, particularly mica papers less than 20 microns thick.

THE DRAWINGS In the drawings FIG. 1 is a diagram of a process beginningwith the preparation of raw material feed and leading through asplitting step and production of a fluid particle suspension to a finalproduct molding step, with or without a separate interveningagglomeration step.

FIG. 2 illustrates the amount of water which is lost from a typicalsample of mica by heating it to progressively higher temperatures untila constant anhydrous weight is reached.

FIG. 3 shows the volume increase of mica in relation to the timeemployed in heating it from 18 C. to 885 C., i.e., the effect of rate ofheating on the degree of swelling achieved.

FIG. 4 is a diagram showing the relationship between the tensilestrength (and also dielectric strength) and the thickness of mica afterit has been bent between two complementary surfaces having a Z-shapedprofile under a load of l kg./cm.2.

FIG. 5 is a representation in vertical section of the Z-shaped deviceused for bending the mica as referred to in FIG. 4.

FIGS. 6A, 6B and 6C are three views showing a piece of mica being splitalong its x and y axes into thin flakes or plates by the simultaneousaction of heat and a high velocity stream of a fluid medium.

FIG. 7 is a microscopic illustration of a group of typical v micaparticles obtained according to a process such as that of Bardet,showing both the irregular shape and wide range of' prevailing particlesizes.

FIG. 8 is a greatly enlarged view showing one of the typical particlesfrom FIG. 7 in vertical section.

FIG. 9 is a microscopic illustration of a group of typical micaparticles made according to the present invention, showing theirpredominantly rectangular shape and relatively narrow size range.

FIG. 9A is a microscopic illustration of a group of mica particles ofultrafine size useful, for instance, in making pigments or fillers.

FIG. 10 is a greatly enlarged view in vertical section of a typicalparticle or flake of this invention, showing its essential flat surfacefree of irregularities.

FIG. I1 is a view in vertical section showing a deposit of relativelythick, inflexible mica particles of the prior art on a solid substrate,with cavities between some of the adjacent particles as well as betweenthe particles and the substrate.

FIG. 12 is a view in vertical section showing a dense deposit of thethin, flat, flexible particles of this invention on and closelyconforming to the surface of a solid substrate comparable to that shownin FIG. 11.

FIG. 13 is a view in vertical section of one embodiment of the apparatusfor disintegrating materials such as mica in accordance with the presentinvention, preferred for use with a r liquid suspension medium.

FIG. 14 is a plan view of the apparatus shown in FIG. i3, taken alongline 14-14.

FIG. 15 is a partial view in vertical section of a variation of theapparatus shown in FIG. 13, wherein product particles are removed fromthe disintegration chamber via a wide spout by electrostatic means,liquid overflow is absent or very small, and the particles areclassified into different fractions according to size.

FIG. 16 is a partial view in vertical section of still another variationofthe apparatus shown in FIG. 313, wherein product particles are removedfrom the disintegration chamber by electrophoresis employing a movingbelt which serves as an electrode to which the product particles adhereand from which they are removed by scraping.

PIGMENTS, FILLERS AND ACTIVE AGGLOMERANTS The term pigment" refers hereto finely divided solids intended for addition to paints, other liquidcoating compositions, glazes and the like while the term filler refersto finely divided solids intended for addition to molding resins,powders, pastes, elastomeric mixtures, graphite compositions, insulatingcompositions, papers as well as layers of free flowing solids such aslayers intended for use as thermal or acoustic insulators. The termagglomerant" refers here to fine mica particles with active surfaces oradsorptive capacities which make them suitable as carriers for activesubstances such as insecticides or herbicides, or as components offiltration media, or as carriers for pigments or other colorants or formaterials such as silver or titanium dioxide powder or the like to makesemiconductive products therefrom. From FIGS. 9 and l0 it is apparentthat mica particles of this invention have the required geometricconfiguration, that is, small thickness and a relatively large and flatsurface, narrow particle size range and large specific surface area.Depending on requirements, the new flakes have a very much higherspecific surface area than similar products made previously, i.e., asurface area in excess of 7 m.2/g., e.g., from above 7 to 700 or even2,500 m.2/g. with certain kinds of mica. The maximum dimension of thenew thin mica flakes or particles can be predetermined in accordancewith requirements and depending on the desired specific surface area maybe of the order of 1 or more millimeters, tenths or hundreds of amillimeter and for special purposes may be of the order of' 1 or moremicrons, tenths, hundreds or even thousands of microns, especially inpreselected narrow size ranges falling within the overall range between30 millimeters down to 2 millimicrons. For instance, the productillustrated in FIGS. 9 and l0 desirably will consist predominantly ofparticles having a high ratio of length to thickness, of the order offrom 1,000/1 to as much as 5 million/ I Pigments, fillers andagglomerants made in accordance with this invention make possible newapplications and new methods of utilization which were not previouslypossible, because the characteristics of the new particles are of afundamentally new kind in the physical sense such that, for instance,the finely divided particles when dispersed in an appropriate fluidbehave like colloids, have a surprising ability to adsorb particles ofother materials on their surfaces, conform tightly to substrates ofvarious configurations without breaking, etc.

PROCESS OF INVENTION Step A Preparation of Raw Material All availableforms of mica, natural or synthetic, may be used in the presentinvention. The raw mica is cleaned in any conventional manner to removeorganic matter, dirt and foreign mineral, preferably to obtain a feed ofat least percent purity. One of the important advantages of the presentinvention is that it permits simultaneous processing of mixtures of micacrystals differing from each other in chemical composition and having awide particle sze range, i.e., mixtures of large and small pieces.

Step B Cleavage or Delamination The method of effecting selectivelyoriented cleavage of mica in accordance with the present invention isillustrated in FIGS. 6A, 6B and 6C. Sudden local temperature effects areindicated by arrows c in FIG. 6B while the effects of the high velocityand high frequency fluid stream are indicated by arrows a and b in FIGS.6B and 6C, and these bring about perfect cleavage of the micapredominantly in two directions, i.e., primarily along the plane oflowest cohesionlthe basic plane) and further along the plane having thenext lowest cohesion which substantially is perpendicular to the firstplane. The effects in other directions are not greatly developed and aresuppressed by the elasticity of the mica and are therefore so weak thatpredominantly they do not reach values necessary for disrupting themechanical cohesion of the mica in any further, less easily splittabledirections.

According to this method the continually fed pieces of mica (FIG. 6A)are exposed to the necessary mechanical, delamination forces, orcombination of mechanical and thermal forces, in one or more splittingchambers which are arranged in series or in parallel. The forces, attemperatures between as low as about C. and up to about I,350 C., act onthe large pieces of feed material for periods which depending onindividual particle size may range from a fraction of a second to a fewminutes within a fluid, and preferably inert,

medium. The forces cause splitting ofthe mica predominantly in thedirection of two planes, by the pulsating, vibrating and accelerating ordecelerating streams of the medium which whirl in a distinctly orientedmanner and which cause delamination predominantly progressively from thesurface of the mica inward as indicated in FIGS. 6B and 6C until theoriginal pieces are delaminated to the desired extent. For some kinds ofmica and some kinds of end use the method may be performed in a singlechamber whereas in other cases the splitting may be effected in aplurality of like or different splitters, e.g., first at ambienttemperature in a liquid medium and then at elevated temperature in lagaseous medium. This method may of course be modified in that, forinstance, the pieces of mica being'fed to the splitter may be preheatedor thermally pretreated prior to introduction into the splitter chamber,preferably in an inert or protective fluid such as argon or hydrogen.

The resulting flaked or disintegrated products having active surfaces(i.e., an adsorptive surface), which they obtain by virtue of theirpredetermined geometric dimensions, are immediately and continuouslyseparated and transferred to the next step. In some cases one may addbinders or other additives such as organic or inorganic fibers,platelets and the like in order to distribute them uniformly in theeventual product.

ln making pigments, fillers and agglomerants of the kind illustrated inFIG. 9A, rather than the predominantly twodimensional flakes illustratedin FIGS. 9 and lill, it is necessary to split the mica as much aspossible not only along the first and the second splitting or fissioningplanes in order to obtain the greatest possible specific surface area,but also to further split the mica to form an ultrafine particle size.

'Ihe ultimate size may be specified in terms of the maximum permissibledimension or diameter or better in terms of the permissible particlesize range, e.g., l to 30 microns, or 0.1 to l micron, etc.Consequently, the splitting method is oriented for splitting accordingto all planes of fission and for producing the smallest particle sizepossible it can utilize further effects of the high velocity of thesplitting medium, 100 meters per second or more, and high frequencywaves (2O kilocycles per second or more) and the acceleration anddeceleration of the particles and the consequent cavitations. The methodcan be still more effective when the splitting medium enters into thereaction chamber intermittently and thus produces pulsations. Theapparatus illustrated in FIGS. I3 to il@ are equipped with devices forthe production of the aforementioned effects, such that pigments,fillers or agglomerants of various sizes and ratios of length orparticle size to thickness may be produced by adjustment of theappropriate variable or variables, eg., by increasing the velocity ofthe fluid medium, by increasing the number of operating jets, etc.

Step C Preparation of Fluid Suspension The mica particles having activesurfaces are kept in or conducted to and maintained in a fluidsuspension in the previously present or in a different protectivemedium. Various combinations of gaseous or fluid media are possibledepending principally on the requirements of subsequent utilization. ltis possible to make intermediate products in a continuous manner and toconcentrate the suspension and only adjust the consistency orconcentration of the suspension prior to the next processing step anddepending on the requirements of the latter. The maintenance of theseparticles as a suspension is advantageously effected with the stream ofthe aforesaid medium, and only by mechanical means, but in some cases itmay be useful to employ additionally the effect of an electrical field.

The suspension of particles of the proper concentration can then becontinuously or intermittently added to an appropriate agglomeratng stepor it can be added directly to some other finishing step.

Product l Fillers, Pigments and agglomerants,

Fillers, pigments and agglomerants, i.e., mica particles which can beadded to coating compositions, electrical putty, synthetic resins,rubber compositions, etc. can have two different forms, that is, eitheras a loose conglomerate of various shapes such as a block from which adesired amount of pigment can be easily broken off for use,` or as afree flowing pulverulent mass. An agglomerant made as outlined above inStep C can be a final product as such. If it was made from a gaseoussuspension it does not require any finishing operation or it may beclassified into fractions of different size in the dry state in anyotherwise known manner. If it was made from a liquid suspension,finishing operations can comprise concentration or compacting anddrying, or if necessary, the particles can be classified while wet priorto compacting in any otherwise known manner. The production of particlesin a free flowing state from a gaseous suspension requires essentiallyonly contacting them with the ordinary atmosphere while beingcirculated, whereby the adhesive surface properties are destroyed,whereas in the case of a liquid suspension a drying step will usually berequired.

APPARATUS Splitter Referring to FIGS. 113 and ld, the apparatus is anaxially symmetrical splitting chamber in the shape of an invertedtruncated cone 5U of circular cross section. I-Iowever, chambers ofother axially symmetrical configurations, e.g., charnbers having ahorizontal cross section. which is quadrangular, octagonal, etc. orwhich has parallel rather than diverging sidewalls are also usable.Incompletely split pieces of mica are recirculated back into thesplitting zone in the direction of the main vertical axis. This deviceis particularly intended for splitting mica in a liquid medium such aswater or ethyl alcohol though it is possible to operate it with agaseous medium. It can be operated either at ambient temperature, or theoperating temperature may be lowered below the freezing point of waterif a suitable nonaqueous fluid medium is used or it can be increased,eg., above the temperature at which mica splits out bound water.

Vessel 50 is provided with a cover 5l which in its central portioncontains a funnel 52 for feeding the pieces of mica which are to besplit. Tubular element 53, which preferably has the shape of a flaredcylinder or cone, is spaced from orienting element 54 which is attachedto and spaced from the sidewall of vessel 5l). A rotating assembly ofhinged splitting elements or paddles 55 is spaced above a rotatablesupporting plate 56. The paddles 55 are hingedly and movably supportedon pivots 57 which are attached to plate 56. The entire splittingassembly is rotated by motor 5h. Vertically arranged baffles or ribs 59are arranged in the upper part of chamber 50 and are attached both tothe outer wall of chamber 50 and to tubular element 53. Sonic orultrasonic vibrators 60 are attached in the outer wall of chamber 5l)facing the orienting element 54k At the bottom of vessel 5@ is a drain6l with valve 62 which may be used for periodic cleaning of the vesselor otherwise as needed.

In the upper part of chamber 50 there is a collector and overflow spoutfor the finished product. In the bottom circumference of vessel 50,facing the exterior faces of revolving elements 55, there is arranged adirectional element or ring M. The pivoted members 55 are easilyremovable such that they may be replaced with members of differentconfigurations, and the total number of the members can also be varied.The shape and quality of the working vertical surfaces 65 and 66 aresuch that they form a resilient system of channels of outwardlynarrowing horizontal cross section. When rotating the members form asystem of essentially vertically oriented planar streams of thesplitting medium flowing radially outward between adjacent members. Itispossible to regulate the mutual relationship of the lower portion of thewalls of filler tube 53, the directional element 5d and the workingsurfaces of members 55 by displacing these elements relative to eachother and thereby vary the flow pattern in the unit. Individual parts ofthe equipment are made from appropriate structural materials such asstainless steel or other metal, synthetic resins, etc. The unit may bevirtually of any size. For instance, it is possible to build smalllaboratory type units with splitter chambers having a bottom diameter ofabout 35 cm. or less and a height of, for instance, 50 cm.; or largecommercial units with splitter chambers having a bottom diameter aslarge as l or 2 meters or more and a height of 3 to l0 meters or more.

In operation, cleaned chips or pieces of mica of whatever kind andthickness and size are continuously fed into funnel 52. The requiredamount of liquid, for instance 500 parts by weight per part of micafeed, is also preferably added through funnel 52. The mica feed andcleavage medium are then aspirated by the rotating effect of elements55, partially from supply tube 53 and partially from the space betweenthe inner wall of directional element 54 and the lower portion of supplytube 53 where insufficiently disintegrated particles are recirculatedinto the splitting zone until they are comminuted to the desired size.

The intensity of the cleavage action can be controlled by the speed ofrotation of the rotor assembly 56, the width and configuration of thechannels formed between adjacent elements 55 and between the outer facesof these elements and the outer ring 64, by the viscosity of thesplitting medium, etc. For instance, the assembly carried on plate 56may rotate at about 20 to 500 r.p.m. or more and the contracting widthof the channels between individual elements 55 may range from as much as50 mm. near the center of the vessel to l mm. or less near theperiphery. It will be understood of course that the width of individualchannels varies in operation and that the narrower the exit of thechannel the more effective will be its splitting action as thevertically oriented mica particles are carried therethrough in thecirculating fluid.

This apparatus has the important advantage that as the mica raw materialis sucked in between the splitting elements 55 it becomes oriented inaccordance with the principal surface of each piece of feed, essentiallyparallel to the direction of the fluid flow through the aforementionedchannels and the laminar surfaces of the resulting fluid streams.Essentially the pieces retain this orientation throughout the entiresplitting process both between the elements 55 and after tangentialdischarge from the channels and passage along directional ring 64, andup into the upper part of the vessel, and even when vibrators 60 areoperating. This orientation prevails both in the case of freshly addedpieces of mica and in the case of pieces which are recirculated.

The splitting elements 55 form in the course of a process a resilientassembly with highly effective working surfaces which are self-cleaningand therefore cannot become obstructed and which can be easily regulatedand simply increased by increasing the diameter and/or height of theelements, by increasing their surface (as shown at 65a and 66a) and byincreasing their total number.

The total effective working surface can also be increased by increasingthe surface of the directional elements 54 and 64. The effectiveness ofthe cleavage operation may be further increased by placing vibrators 60in operation.

The cleavage effects are based principally on the effect of the highvelocity laminar plane streams of the fluid medium acting essentiallyparallel to the major surfaces of the oriented mica particles. Thevelocity of the stream in this process increased in the centrifugaldirection while the thickness of the channels and hence the laminarfluid streams flowing therethrough decrease in the radially outwarddirection. Being resilient, individual channels become narrower or widerduring operation depending on the thickness of the pieces of micapassing through them.

A shape of the splitting elements such as that illustrated at 65a and66a additionally provides a sort of delaying chambers and increases thenumber of the narrowest channels or passages through which the mica isdragged in the process. This produces a pulsating flow and furtherenhances the cleavage action.

The velocity of the fluid stream changes according to channel crosssection and is therefore usually lowest in the central part of thevessel and conversely highest in the peripheral portions. Mica is thussplit by the effects of a fast laminar stream of fluid and the changesin its velocity, i.e., its acceleration and decelerating, by the rapidincrease in velocity of the fluid stream in the radially outwarddirection, the resulting cavitation and vibration or pulsation alongsinusoidal faces 65a and 66a, the slowing down along the effectivesurface, etc. When these effects are insufficient to achieve the desireddegree of comminution in any particular case the cleavage action may befurther intensified by the use of devices 60 which may produce sonic oreven ultrasonic vibrations, etc., vibrations in the range from about lOkc./sec. up to about l mc./sec.

The split particles having the desired dimensions are continuouslysorted out from the process as soon as they reach the desired size,being floated up and removed in the overflow of the liquid through spout63 and then transferred to whatever further operation may be desired.The principal variable by which circulation and recirculation of theparticles Within the splitting chamber is controlled, is the speed ofrotation of the revolving assembly in the bottom, but rate ofcirculation of liquid through the unit can also be adjusted to cause thedesired range of particle sizes to be floated out of the unit.

Instead of removing the comminuted particles in an overflowing stream ofthe liquid medium as shown in FIG. 13, it is possible to remove themwithout virtually any liquid by using an arrangement as shown in FIGS.15 or 16. As shown in FIG. 15, the liquid medium is maintained in thesplitting chamber 50 with no or virtually no liquid addition or overflowwhile two-spaced electrodes are arranged at the overflow spout 63 suchthat the particles of mica product become charged near the liquidsurface in the splitting chamber and then jump out from the liquid bybeing attracted to the other electrode whence they are finally removed.An inert gas such as argon or neon may be maintained in such a system toavoid any degradation of the product particles by contact with air oroxygen. By arranging a series of collecting bins beneath the twospacedelectrodes, the mica particles being ejected from the splitter cansimultaneously be classified into several fractions according to theirweight, the heaviest particles dropping out first and the progressivelyfiner ones dropping down at more distant points from the spout.

In an alternative arrangement, illustrated in FIG. 16, a moving belt maybe arranged in the upper portion of the splitter and an electric fieldset up such that the product particles become charged near the top ofthe liquid medium in chamber 50 and then are carried by electrophoresisto the oppositely charged moving belt to which they remain attacheduntil they are scraped off and recovered. Example l A mixture containingabout equal proportions of clean pieces of muscovite and phlogopiteabout 3 to 100 mm. in diameter is introduced into the funnel 52 of theapparatus in FIG. 13. 800 parts of clean water per part of mica issimultaneously introduced and the mixture of mica particles and water isaspired between the jaws of the rotary elements at the bottom of thesplitter and the mica is thus split into small particles in accordancewith its laminar structure by the action of the water stream and theauxiliary high frequency means 60 vibrating at kc./sec. The rotorrevolves at 100 r.p.m. When a particle reaches a specific surface areaof 5 mF/g. it is immediately sorted'out from the process by floating upin the water whereas coarser particles settle out from the water streamand return downwardly toward the rotating elements for furtherdisintegration.

The resulting suspension of mica flakes of proper size overflows into astorage vessel (not shown in FIG. 13) and then, after adjustment ofproper solids concentration, into the chamber of a paper making machine.

The new mica products described herein are substantially better in termsof their mechanical, electrical and other physical properties, thansimilar mica products heretofore available, generally several timesbetter, such that in effect new classes of mica products having newtypes of utility are now made available. The advantages are particularlyapparent in fabricated products made from the new basic material, i.e.,the ultrafine mica flakes. For instance, because of the extremely smallthickness of the new mica flakes, it now becomes possible to makeself-supporting coherent mica webs, coatings and laminates only a fewmicrons thick.

The key pieces of equipment designed in accordance with this inventionhave large capacity and relatively small dimen sions, such that as muchas ten times more production can be obtained from a given plant areathan heretofore, Moreover, the disintegration or cleavage technique ofthis invention is unusually advantageous in that it permits thesimultaneous utilization of different kinds of mica such as muscoviteand phlogopite, it also permits the use of a mica feed containing a widerange of particle sizes, and in all of this it makes possibleessentially l() percent conversion of the feed material into desiredproducts.

The methods and apparatus of the invention further make it possible tomake combination products from mica and various other materials such asglass fibers or platelets, fibers of asbestos, silica, cellulose orsynthetic fiber forming resins, glass cloth, binders, foils of syntheticresins or metals, etc. Because of their high surface area, the novelmica particles themselves offer unusual advantages as pigments, fillersand also as carriers for other pigments and for physiologically activesubstances and catalytic substances. Because of the extremely smallthickness, coatings or compositions made from these new mica particleshave far superior barrier effects, novel decorative effects, etc.

As compared with similar products known previously, the ultradelaminatedflakes made in accordance with this invention are such that they fallinto a quite different and new physical field and are therefore governedby different physical laws than the earlier products. One of thepredominant characteristics of the new particles is that they behavelike colloids in a suitable liquid medium. Their sedimentation times areextremely long, such that they can be used in processes where thecoarser, previously available particles were useless or gave poorresults.

ln addition to the aforementioned product properties, importantadvantages are obtained in that certain features of the presentinvention permit a very high degree of flexibility ofthe process,permitting the economical use of different types of splitters inparallel or in series depending on types of products required, and highproduction capacity per unit area.

lt should be understood that the foregoing general description andspecific examples have been given primarily for purposes of illustrationand that numerous variations and modifications thereof are possiblewithout departing from the scope or spirit of the disclosed invention.lt should also be understood that, in the absence of indications to thecontrary, all percentages and proportions of materials are expressed inthe disclosure on a weight basis.

rfhe scope of the invention is particularly pointed out in the appendedclaims.

ll. A process for ultradelaminating a crystalline laminar solid intothin flakes which comprises:

a. forcing a fluid medium through apertures having narrow elongatedcross section in a bottom portion of a conversion zone, said aperturesbeing oriented substantially parallel to the height of said zone, andthereby forming in said bottom portion a system of whirling tluidstreams having an orientation approximately parallel to the apertures,

b. introducing relatively coarse pieces of said solid into saidconversion zone whereby said pieces become suspended in said whirlingstreams and disintegrated principally in planes corresponding to theprincipal two axes of the solid crystal lattice,

c. circulating the resulting fluid suspension comprising comminutedsolid from said bottom portion upwardly in the peripheral portion ofsaid zone into an Lipper portion thereof,

ll il d. settling insufficiently comminuted solid particles from saidupwardly circulating suspension back into said bottorn portion forfurther disintegration in said whirling streams,

c. removing solid particles of the required fineness from the upperportion of said conversion zone.

2l. Process for disintegrating mica into thin flat flakes whichcomprises suspending relatively coarse pieces of mica in an essentiallyinert liquid, in a proportion of l part of mica per 5 to 5,000 parts ofliquid, in a bottom portion of an upwardly expanding conversion zonehaving substantially the shape of a truncated cone, propelling themixture near the bottom of said conversion zone in a centrifugaldirection through constricted substantially vertical channels having avarying width such that the mixture becomes more constricted as itpasses therethrough, circulating the mixture upwardly along theperiphery of the conversion chamber such that mica particles having thedesired fmeness rise to the: top and overflow from said conversion zoneto be recovered while insufficiently fine particles settle downwardtoward the: central portion of the conversion zone for further passagethrough said narrow channels for further disintegration.

El. A process according to claim 2 wherein said channels havealternating areas of larger and narrower width.

d. A process for ultradelaminating a crystalline laminar solid into thinflakes which comprises:

a. forcing a liquid medium through apertures in a bottom portion of agenerally circular conversion zone, said apertures being normal to theheight of said zone whereby said liquid forced through said apertures insaid bottom portion forms a system of whirling streams having anorientation approximating the circular path of said conversion zone,

b. introducing relatively coarse pieces of said solid into said systemof whirling liquid streams and thereby disintegrating said piecesprincipally in planes corresponding to tlie principal two axes of thesolid crystal lattice,

c. circulating the resulting liquid suspension comprising comminutedsolid from said bottom portion upwardly in the peripheral portion ofsaid zone into an upper portion thereof,

d. recirculating insufficiently comminuted solid particles from saidupwardly circulating suspension back into said bottom portion forfurther disintegration in said whirling streams,

e. removing solid particles of the required fineness from saidconversion zone.

5. A process for disintegrating mica into thin flat flakes whichcomprises feeding a suspension of insufficiently fine pieces of mica inan essentially inert liquid to a bottom portion of an upwardly extendingconversion zone having a substan tially circular cross section,propelling the mixture near the bottom of said conversion zone in acentrifugal direction through constricted channels having substantiallyvertical walls and having a resiliently varying width such that themixture becomes more constricted as it passes therethrough, circulatingthe mixture upwardly in the conversion zone such that mica particleshaving the desired fineness rise to the top and are recovered from saidconversion zone while insuffi ciently fine particles settle downwardtoward the central portion of the conversion zone for further passagethrough said narrow channels for further disintegration.

ti. A process according to claim 5 wherein said channels havealternating areas of larger and narrower width.

"1'. A process according to claim 5 wherein said mica particles arerecovered from said conversion zone by electrostatic means.

A process according to claim 5 wherein said mica particles are recoveredby flotation.

il. An apparatus for disintegrating solids suspended in a liquid mediumcomprising a vessel having a sidewall of generally circular crosssection and providing a disintegration chamber in the lower portionthereof and an elutriation zone in the upper portion thereof,disintegration means in said chamber comprising a plurality ofchannel-forming members having substantially vertical walls extendinggenerally radially outward from the central area of said chamber, saidchannelforming members forming channels of resiliently varying widthgenerally narrowing from said central area toward the periphery of saidchamber and terminating short of said periphery, means mounting saidchannel-forming members for rotation in said chamber and meansoperatively connected therewith for rotating said members, said vesselincluding means for introducing solids in liquid medium into the centralarea of said chamber and means of withdrawing product from

2. Process for disintegrating mica into thin flat flakes which comprisessuspending relatively coarse pieces of mica in an essentially inertliquid, in a proportion of 1 part of mica per 5 to 5,000 parts ofliquid, in a bottom portion of an upwardly expanding conversion zonehaving substantially the shape of a truncated cone, propelling themixture near the bottom of said conversion zone in a centrifugaldirection through constricted substantially vertical channels having avarying width such that the mixture becomes more constricted as itpasses therethrough, circulating the mixture upwardly along theperiphery of the conversion chamber such that mica particles having thedesired fineness rise to the top and overflow from said conversion zoneto be recovered while insufficiently fine particles settle downwardtoward the central portion of the conversion zone for further passagethrough said narrow channels for further disintegration.
 3. A processaccording to claim 2 wherein said channels have alternating areas oflarger and narrower width.
 4. A process for ultradelaminating acrystalline laminar solid into thin flakes which comprises: a. forcing aliquid medium through apertures in a bottom portion of a generallycircular conversion zone, said apertures being normal to the height ofsaid zone whereby said liquid forced through said apertures in saidbottom portion forms a system of whirling streams having an orientationapproximating the circular path of said conversion zone, b. introducingrelatively coarse pieces of said solid into said system of whirlingliquid streams and thereby disintegrating said pieces principally inplanes corresponding to the principal two axes of the solid crystallattice, c. circulating the resulting liquid suspension comprisingcomminuted solid from said bottom portion upwardly in the peripheralportion of said zone into an upper portion thereof, d. recirculatinginsufficiently comminuted solid particles from said upwardly circulatingsuspension back into said bottom portion for further disintegration insaid whirling streams, e. removing solid particles of the requiredfineness from said conversion zone.
 5. A process for disintegrating micainto thin flat flakes which comprises feeding a suspension ofinsufficiently fine pieces of mica in an essentially inert liquid to abottom portion of an upwardly extending conversion zone having asubstantially circular cross section, propelling the mixture near thebottom of said conversion zone in a centrifugal direction throughconstricted channels having substantially vertical walls and having aresiliently varying width such that the mixture becomes more constrictedas it passes therethrough, circulating the mixture upwardly in theconversion zone such that mica particles having the desired finenessrise to the top and are recovered from said conversion zone whileinsufficiently fine particles settle downward toward the central portionof the conversion zone for further passage through said narrow channelsfor further disintegration.
 6. A process according to claim 5 whereinsaid channels have alternating areas of larger and narrower width.
 7. Aprocess according to claim 5 wherein said mica particles are recoveredfrom said conversion zone by electrostatic means.
 8. A process accordingto claim 5 wherein said mica particles are recovered by flotation.
 9. Anapparatus for disintegrating solids suspended in a liquid mediumcomprising a vessel having a sidewall of generally circular crosssection and providing a disintegration chamber in the lower portionthereof and an elutriation zone in the upper portion thereof,disintegration means in said chamber comprising a plurality ofchannel-forming members having substantially vertical walls extendinggenerally radially outward from the central area of said chamber, saidchannel-forming members forming channels of resiliently varying widthgenerally narrowing from said central area toward the periphery of saidchamber and terminating short of said periphery, means mounting saidchannel-forming members for rotation in said chamber and meansoperatively connected therewith for rotating said members, said vesselincluding means for introducing solids in liquid medium into the centralarea of said chamber and means of withdrawing product from saidelutriating zone.
 10. An apparatus according to claim 9 wherein saidvessel includes baffle means above said channel-forming means andseparating said disintegration chamber and elutriation zone from oneanother.
 11. An apparatus according to claim 10 wherein said bafflemeans includes a wall surface adjacent and parallel to the sidewall ofsaid vessel for guiding disintegrated particles upwardly along theperipheRy of said sidewall as the particles are circulated from saidchamber to said elutriating zone.